Various display devices are equipped for stereo viewing. Unlike mono viewing, stereo viewing involves the display of separate content for the right and left human eye. Specifically, such stereo viewing requires the presentation of a separate image to the left and right human eye. In one particular type of stereo viewing, namely time sequential stereo viewing, such left and right images are presented in an alternating manner. To ensure a proper stereo viewing experience, stereoscopic glasses are also typically used which make the left image only visible to the left eye and the right image only visible to the right eye at the appropriate time [e.g. in response to a vertical synchronization (Vsync) signal, etc.].
In the past, time sequential stereo viewing has worked well on CRTs and related displays [e.g. high frame rate (DLP) projectors, etc.]. However, time sequential stereo viewing has not shown promise with liquid crystal displays (LCDs), whether flat-panel or in the form of a projector, due to several issues. For example, the nature of the LCD update process unfortunately results in only short periods of time when the right image and left image may be present in their entirety, as will now be described in more detail.
FIG. 1 illustrates hypothetical shortcomings that would exist if stereo viewing were attempted utilizing an LCD. As shown in the present hypothetical example, the LCD would receive pixels in raster scan order (i.e. left to right, line by line from top to bottom, etc.) over a cable 10, such as a digital video interface (DVI) or video graphics array (VGA) cable. A first left image. L1 intended for viewing by a left eye is sent over the cable 10 first. Thereafter, there is a pause in transmission called the vertical blanking, interval, after which a first right image R1 intended for the right eye is sent, and so forth.
Unlike CRTs and other related displays, LCD pixels have individual capacitive storage elements that cause each pixel to retain its color and intensity until it is updated by LCD driver-related electronics, which addresses pixels in raster order. Thus, at time T1, when part of the first right image R1 has been sent, the actual image emitted from the LCD screen includes the ‘not yet overwritten’ (e.g. red) part of first left image L1 at the bottom, and the newly written (e.g. green) part of the first right image R1. Further, at T2, the display includes only the first right image R1. At time 13, the first right image R1 has been partially overwritten by a second left image L2, in the manner shown. To this end, if the display content at time T1 and 13 were shown to the right or left eye, such eye would unfortunately receive content, at least in part, not intended for such eye.
As mentioned earlier, stereoscopic glasses equipped with right and left eye shutters are often employed to ensure that the proper eye views the appropriate image, during stereo viewing. As shown, in the present hypothetical example, after the first right image R1 starts to be displayed, a right eye shutter control 20 switches the right shutter to an open orientation in response to an associated Vsync signal 40A (during which a left shutter is maintained in a closed orientation). Similarly, after a subsequent left image L2 is displayed, a left eye shutter control 30 switches the left shutter to an open orientation again in response to the associated Vsync signal 40B (at which time the right shutter toggles to and is maintained in a closed orientation).
Again, each eye unfortunately, receives content, at least in part, not intended for such eye for a sizeable portion of the duration in which the associated shutter is in the open orientation, resulting in unacceptable stereo viewing. While a post-Vsync, fixed delay has been used in prior art systems for addressing this issue, there is still a continuing need for dealing with this and/or other problems associated with the prior art.